Telephone sets are often, except for the common elements such as the handset, a signalling device and a dial or set of push-button necessary for the ordinary telephoning function, provided with additional arrangements, for example, for internal communication and signalling needs, loudspeaking function etc. These arrangements are located in the fixed part of the set which must be dimensioned with sufficient space for them. It is, however, desirable both by the telephone industry and the telephone administrations to keep the number of telephone set models as low as possible. Therefore efforts have been made to construct sets provided for various types of telephone versions within the same cover configuration. Most telephone sets in the telephone networks are, however, the common telephone sets without auxiliary equipment. These sets will then contain a space which is not used for the telephone technical components included.